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Ch16 Electrolysis - Coggle Diagram
Ch16 Electrolysis
Electrolytes
(l) or (aq)
Passage of electricity
Chemical decomposition
Process of electroysis
Ions attracted to electrode that has opposite charge
During electrolysis
Metal and H+ ions are cation
To cathode (-)
RED CAT
Non-metal ions except H+ are all anions
To anode (+)
AN OX
Electrolysis of (aq) electrolytes/inert electrodes
Soluble ionic compounds
Dissolve in H2O to give mobile ions
Some covalent compounds ionize in H2O to produce ion
Pure H2O can only ionize slightly
H2O -> H+ + OH-
One kind of ions discharge first
Preferential discharge
Factors
Position in ECS
Concentration of electrolyte
Nature of elctrodes
Discharge of cations +
Lower in ECS is preferentially discharged
As they are stronger oxidizing agents, gaining e- more readily
In (aq) solution, cations higher than H+ in ECS are usually not discharged
2 more items...
K+
Ca2+
1 more item...
Increasing ease of discharge
1 more item...
Weak oxidizing agent
Discharge of anions -
Higher in ECS preferentially discharged
As they are stronger reducing agents, loses e- more readily
Anions lower than OH- usually are not discharged
2 more items...
OH-
I-
1 more item...
Strong reducing agents
Relationship between concentration and the preferential discharge of ions
With similar concentrations
OH- higher than Br- (stronger reducing agent)
OH- discharged (cathode)
2 more items...
H+ discharged (anode)
2 more items...
If concentration of Br- > OH- a lot
Br- discharged
For concentrated NaCl
H+ discharged at Cathode
At anode, 2Cl- discharged
1 more item...
O2 sometimes at anode
H2 sometimes at cathode
Electrolysis of molten electrolytes/inert elctrode
Inert electrodes: C/Pt
Does not react
Electrolyte
Molten, no water
Insoluble ionic compound are usually melted
Electrolytic cell
Decomposition by electricity
Redox reaction forced to occur
AN OX, RED CAT
-ve(anode) of chem cell to -ve(cathode) of electrolytic cell
+ve(anode) of electrolytic cell to +ve(cathode) of chem cell
One type of electrolyte
Immersed in same electrolyte
Observable change: fast
e- flow